Identity and relationships of the Arboreal Caatinga among other floristic units of seasonally dry tropical forests (SDTFs) of north‐eastern and Central Brazil

Abstract

The tree species composition of seasonally dry tropical forests (SDTF) in north-eastern and central Brazil is analyzed to address the following hypotheses: (1) variations in species composition are related to both environment (climate and substrate) and spatial proximity; (2) SDTF floristic units may be recognized based on peculiar composition and environment; and (3) the Arboreal Caatinga, a deciduous forest occurring along the hinterland borders of the Caatinga Domain, is one of these units and its flora is more strongly related to the caatinga vegetation than to outlying forests. The study region is framed by the Brazilian coastline, 50th meridian west and 21st parallel south, including the Caatinga Domain and extensions into the Atlantic Forest and Cerrado Domains. Multivariate and geostatistic analyses were performed on a database containing 16,226 occurrence records of 1332 tree species in 187 georeferenced SDTF areas and respective environmental variables. Tree species composition varied significantly with both environmental variables and spatial proximity. Eight SDTF floristic units were recognized in the region, including the Arboreal Caatinga. In terms of species composition, its tree flora showed a stronger link with that of the Cerrado Dry Forest Enclaves. On the other hand, in terms of species frequency across sample areas, the links were stronger with two other units: Rock Outcrops Caatinga and Agreste and Brejo Dry Forests. There is a role for niche-based control of tree species composition across the SDTFs of the region determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal-limited tree flora. These units should be given the status of eco-regions to help driving the conservation policy regarding the protection of their biodiversity.

Tree species composition in areas of Atlantic Forest in southeastern Brazil is consistent with a new system for classifying the vegetation of South America

“…It is well known that plant species distribution varies worldwide across vegetation physiognomies, climatic conditions and elevational gradients (Holdridge 1947;Ledru 1993;Oliveira-Filho & Fontes 2000;Gaston 2003;Santos et al 2012). We also know, more specifically in the Atlantic Forest Biome, that a number of factors, such as precipitation, temperature and altitude, affect the distribution of tree species (Oliveira-Filho & Fontes 2000;Oliveira-Filho et al 2005;Oliveira 2006;Cerqueira 2011;Marques et al 2011;Santos et al 2011).…”

First avifaunal survey of a Cerrado dry forest enclave on the right bank of the São Francisco River, Minas Gerais, Brazil, with insights on geographic variation of some species

“…Seasonally dry tropical forests (hereafter SDTFs) present a circum-Amazonian distribution in South America and have been the main focus of many recent biogeographic and conservation studies (e.g., Prado & Gibbs, 1993;Espírito-Santo et al, 2009;Pennington et al, 2000Pennington et al, , 2006Pennington et al, , 2009Zanella, 2010;Werneck, 2011;Werneck et al, 2011;Santos et al, 2012;Arruda et al, 2013;DryFlor, 2016). These forests are usually associated with fertile soils and with climates marked by highly seasonal rainfall with a severe dry season of three to six months, when most of the vegetation is leafless (Pennington et al, 2006;DryFlor, 2016).…”

“…These "islands" were named "Cerrado dry forests" by Santos et al (2012) and are very important from a biogeographical point of view, since they suggest historical connections among several SDTF nuclei (Werneck & Colli, 2006).…”

“…Olmos (2005) also included Lepidocolaptes wagleri (Wagler's Woodcreeper) as an endemic of these dry forests. Another species, Phylloscartes roquettei (Minas Gerais Tyrannulet), was considered endemic to these dry forests (Stattersfield et al, 1998;Olmos, 2005), but it has been recently recorded in gallery forests and arboreal caatingas, a deciduous forest occurring along the hinterland borders of the Caatinga province (sensu Santos et al, 2012), located east to the Espinhaço Mountain Range (Luiz et al, 2006;Santos et al, 2009).…”

Flower development ofGoniorrhachis marginatareveals new insights into the evolution of the florally diverse detarioid legumes

“…The genus is represented by just G. marginata, which is a 5-15(-30)-m high evergreen tree that often dominates the disjunct patches of seasonally dry tropical forests or arboreal caatinga, especially on richer soils and along temporary rivers, from Sergipe and Bahia to Minas Gerais, Espırito Santo and northern Rio de Janeiro ( Fig. 2A; Queiroz, 2006Queiroz, , 2009Santos et al, 2012;Oliveira-Filho, 2014;. The flowers of G. marginata are characterized by their long hypanthium with an adnate gynoecium on the rim, and by the radially symmetric corolla and diplostemonous androecium superficially resembling Rosaceae flowers (Figs 1 and 2).…”